Viscous liquids such as adhesives and sealants are typically shipped into factories and other industrial sites in cylindrical drums ranging in size and capacity from a few gallons to several hundred gallons. These containers are usually made of steel and have a lid which is removed when access to the viscous liquid is desired.
It is generally considered impractical to transfer viscous sealants and adhesives from their shipping containers into an intermediate container for dispensing; i.e., it is generally considered preferable to provide a dispensing system which is capable of cooperating with the original shipping container to remove and dispense the liquid directly therefrom. One type of container-compatible dispensing system comprises a base, a frame erected on the base for receiving therein an open-ended upright container of viscous material, a ram plate which is typically disc-like in configuration and adapted to enter into the open end of the container in close and conforming relationship to the walls of the container, and a vertically travelling elevator system which allows the ram plate to be raised and lowered relative to the container. A positive displacement pump is carried by the ram plate and has an intake portion, generally called a "shovel", depending from the bottom surface thereof so as to enter into the viscous liquid when in the operative arrangement. As the material is depleted from the container, the elevator system maintains a positive pressure on the fluid by gradually lowering the ram plate into the container.
Although prior art systems of the type described have been satisfactorily used, there are a number of areas in which difficulties can be encountered. These area include: maintaining proper alignment between RAM the plate and the container axis, maintaining an adequate seal between the edges of the ram plate and the sidewalls of the container, experiencing difficulty in withdrawing the ram plate from the container at the end of a dispensing operation and such other secondary problems as excessive noise from the cyclical operation of the power source for the positive displacement pump. These problems tend to magnify when larger containers are used.
Also by way of background, the preferred positive displacement pump for viscous fluids is the type disclosed in U.S. Pat. No. 3,995,966 wherein the vertical displacement rod of such pump is connected directly to the pump shovel and the disclosure of said U.S. Pat. No. 3,995,966 is incorporated herein by reference.